What is Junk DNA?

In genetics, the term junk DNA refers to regions of DNA that are noncoding.

DNA contains instructions (coding) that are used to create proteins in the cell. However, the amount of DNA contained inside each cell is vast and not all of the genetic sequences present within a DNA molecule actually code for a protein.

Some of this noncoding DNA is used to produce non-coding RNA components such as transfer RNA, regulatory RNA and ribosomal RNA. However, other DNA regions are not transcribed into proteins, nor are they used to produce RNA molecules and their function is unknown.

The proportion of coding versus noncoding DNA varies significantly between species. In the human genome for example, almost all (98%) of the DNA is noncoding, while in bacteria, only 2% of the genetic material does not code for anything.

Is Most of Your DNA Junk?

The term Junk DNA

The term “junk DNA” was first used in the 1960s, but was formalized by Susumu Ohno in 1972. Ohno noticed that the amount of mutation occurring as a result of deleterious mutations set a limit for the amount of functional loci that could be expected when a normal mutation rate was considered. In a Nature review published in the 1980, Leslie Orgel and Francis Crick stated that junk DNA “had little specificity and conveys little or no selective advantage to the organism."

However, over the years, researchers have found evidence to suggest that junk DNA may provide some form of functional activity. Some lines of evidence suggest that fragments of what were originally non-functional DNA have undergone the process of exaptation throughout evolution. Exaptation refers to the acquisition of a function through means other than natural selection.

In 2012, a research program called the ENCODE project concluded that around three quarters of the noncoding DNA in the human genome did undergo transcription and that almost 50% of the genome was available to the proteins involved in genetic regulation such as transcription factors.

However, these findings have been criticized by other scientists who claim that the accessibility of these genomic segments to transcription factors does not mean they necessarily have any biochemical function or that transcription of the segments is in any way advantageous in terms of evolution.

Further Reading

Last Updated: Nov 29, 2022

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mandal, Ananya. (2022, November 29). What is Junk DNA?. News-Medical. Retrieved on July 18, 2024 from https://www.news-medical.net/life-sciences/What-is-Junk-DNA.aspx.

  • MLA

    Mandal, Ananya. "What is Junk DNA?". News-Medical. 18 July 2024. <https://www.news-medical.net/life-sciences/What-is-Junk-DNA.aspx>.

  • Chicago

    Mandal, Ananya. "What is Junk DNA?". News-Medical. https://www.news-medical.net/life-sciences/What-is-Junk-DNA.aspx. (accessed July 18, 2024).

  • Harvard

    Mandal, Ananya. 2022. What is Junk DNA?. News-Medical, viewed 18 July 2024, https://www.news-medical.net/life-sciences/What-is-Junk-DNA.aspx.


  1. Docteur House Docteur House France says:

    Cela veut dire que notre ADN est le résultat d’un code réfléchi comme un code informatique…

    Il y aurait donc un programmeur ?

    Comme a dit Voltaire “L’univers m’embarrasse, et je ne puis songer que cette horloge existe et n’ait pas d’horloger”. Nous ne devons pas oublier que nous sommes des créatures et qu’il y a un créateur qui nous aime.

  2. David Schiffer David Schiffer Norway says:

    There is no such things as Junk DNA. The vast amount of seamingly non functional DNA is simply a recording of the collective life experiences of our ancestral lines, their complete life experience and understanding. That is why Human DNA has so much more of it than any other species, we learn and understand so much more, the lesser the lifeform, the less data they collect. In short, its genetic memory storage.

  3. Ryan Young Ryan Young United States says:

    When you consider that random molecules may interact with DNA to cause a mutation or switch a gene on or off (e.g. cigarette smoke turning off a cell's self-destruct mechanism, causing that cell to become cancerous), then having segments that do nothing can serve as decoys or armor for segments that are actually important.

  4. James Rawles James Rawles United States says:

    Just because 98% of our genome does not code for protein does not mean it does not encode important information. Our overall gross anatomical structure, from the appearance of our facial features, our internal organs, to our overall body size and layout, is clearly inherited. Where does that 'blueprint' reside? I presume its somehow encoded into DNA. Our genome holds about 1.5 giga bytes of information. I expect it would take a pretty sizeable chunk of that to encode our 3D anatomy! How the information might be actuated is a mystery to me.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.